Monday, October 08, 2007

The Yankees live to fight another day, thanks to some timely hitting by Johnny Damon, a spark on the basepaths by gimpy Hideki Matsui, some lousy defense by Cleveland's Trot Nixon, and fine relief pitching from Philip Hughes. The latter was necessary after Roger Clemens departed in the third inning, trailing 2-0 and having aggravated his injured hamstring. My prediction got the inning right if not the score.

For Game Four, Joe Torre has opted to go back to Chien-Ming Wang, who was tagged for eight runs in Game One. He's appearing on just three days' rest, and his outing wasn't exactly short; 94 pitches under duress is a pretty full workload for 4.2 innings. Anecdotally, sinkerballers such as Wang tend to benefit from being a bit tired. With three days of rest instead of the seven he had prior to the series opener, the Yankees have to hope so.

Just as important as the amount of rest, if not more, is the fact that Wang is pitching at home. I made note of his persistent home-road splits in my series preview at BP and expanded on them here a couple days back. Today at BP, I have a quick and dirty study taking an even closer look at Wang and examining whether groundballers such as Wang tend to fare better at home than on the road:

Looking at the performance record, note the consistent disparity in innings pitched across the two splits. Overall, Wang has thrown 55 percent of his innings at home, suggesting that the Yanks may regard that setup as optimal. Second, while Wang's home/road split has been consistent across all three years, the actual ERA disparity is much, much wider than suggested by his peripherals, as reflected via FIP [Fielding Independent Pitching]; an apparent home-field advantage of 0.14 runs according to FIP turns into a 1.58 run advantage according to ERA. For those wise enough to pooh-pooh the earned/unearned run distinction, the spread is 1.82 runs per nine innings.

The difference appears to be largely due to the results of balls in play. Wang's BABIPs at home have consistently been about 40 points below the league averages (.296, .305, and .308, respectively, over the last three years), enabling him to beat his FIP estimates by 0.78 runs. On the road, his BABIPs have been about 15 points above, with a much wider variation from year to year; collectively, his road ERAs have been 0.66 runs higher than his FIPs.

This discrepancy could be random, but it may not be. Along with the ballpark-to-ballpark variations in fence distances and the amount of foul territory, home/road differences may be a reflection of field preparation. It's no secret that groundskeepers can prepare the field to the benefit of the home team's starting pitcher. For any pitcher, that may include tailoring the mound to his liking. For a groundballer, that may include watering down the area in front of home plate and leaving the infield grass longer; likewise, for an opposing groundballer, the crew may opt to cut the grass short and keep the plate area dry and hard. The TBS broadcast of Game Two of the Cubs-Diamondbacks series showed the Arizona crew watering down home plate before the game even as the umpires looked on. Lou Piniella complained, prompting the umps to order the application of a drying compound, but the results were still reportedly damp. Still, there's an element of tradition involved—such groundskeeping gamesmanship goes back to the 19th century, as teams even back then were watering down the basepaths to slow down their speedier opponents.

Turning to the group of 65 pitchers (including Wang) who threw at least 50 innings at home and on the road in each of the last three seasons -- a group that's decidedly better than league average -- we see:

• a homefield advantage of 0.38 runs of ERA for the entire group of pitchers. That's about twice as large as predicted by FIP (based on the pheripherals), with differential results on balls in play widening the gap.

• a 0.30 ERA advantage for the group's groundballers over the flyballers, mainly due to a lower home run rate.

• a 0.45 ERA advantage for the groundballers at home, as compared to a 0.39 ERA advantage for the flyballers at home, with a separation in favor of the groundballers persisting across the two sets. The ERAs of the four subsets of performers:

Home RoadGB 3.78 4.23FB 4.16 4.45

More detailed breakdowns can be found at the BP, where the piece is free. The take-home message is this:

What this in-no-way-definitive study suggests is that a groundballer pitching at home -- exactly like Wang in Yankee Stadium -- would appear to be the best of the limited permutations available. Further research along these avenues is needed to clarify the matter, but at River Avenue and 161st Street in the Bronx on Thursday night, with the Yankees' continued presence in the postseason and Joe Torre's tenure in pinstripes riding on Wang's performance, it will have to do.